Hydrolysis of chemically distinct sites of human serum albumin by polyoxometalate: A hybrid QM/MM (ONIOM) study

In this study, mechanisms of hydrolysis of all four chemically diverse cleavage sites of human serum albumin (HSA) by [Zr(OH)(PW₁₁O₃₉)]⁴⁻ (ZrK) have been investigated using the hybrid two-layer QM/MM (ONIOM) method. These reactions have been proposed to occur through the following two mechanisms: internal attack (IA) and water assisted (WA). In both mechanisms, the cleavage of the peptide bond in the Cys392-Glu393 site of HSA is predicted to occur in the rate-limiting step of the mechanism. With the barrier of 27.5 kcal/mol for the hydrolysis of this site, the IA mechanism is found to be energetically more favorable than the WA mechanism (barrier = 31.6 kcal/mol). The energetics for the IA mechanism are in line with the experimentally measured values for the cleavage of a wide range of dipeptides. These calculations also suggest an energetic preference (Cys392-Glu393, Ala257-Asp258, Lys313-Asp314, and Arg114-Leu115) for the hydrolysis of all four sites of HSA. © 2018 Wiley Periodicals, Inc.     

Metal-Stabilized [B8H8]2− Derivatives with Dodecahedral Structure in the Solid and Solution States: [(Cp2MBH3)2B8H6] (Cp=η5-C5H5; M=Zr (1-Zr) and Hf (1-Hf)).

Despite the synthesis and structural characterization of closo-hydroborate dianions, [B_nH_n]²⁻ (n=6–12) more than 50 years ago, some ambiguity remains about the structure of [B₈H₈]²⁻. Although the solid-state structure of [B₈H₈]²⁻ was established by single-crystal X-ray studies in 1969, fast rearrangements in solution at accessible temperatures prevented its detailed characterization. We therefore stabilized a derivative of [B₈H₈]²⁻ by using Cp₂MBH₃ and structurally characterized two new octaborane analogues, [(Cp₂MBH₃)₂B₈H₆] (Cp=η⁵-C₅H₅; M=Zr ( 1-Zr ) and Hf ( 1-Hf )), so that the dynamics of the B₈ skeleton were arrested. The solid-state structures of both 1-Zr and 1-Hf comprise a dodecahedron core protected by {Cp₂MBH₃} moieties on both sides of the cluster. Spectroscopic characterization (¹¹B NMR) validates the intactness of the B₈ dodecahedron core in solution as well. Theoretical calculations establish that the two exo-{Cp₂MBH₃} fragments provide structural and electronic structural stability to the B₈ core and its intact dodecahedral dianionic nature. Furthermore, we propose isodesmic equations for the formation of higher analogues of the B_n core (n>8) guarded by different group 4 transition metals. Our analysis suggests that, as we move to higher polyhedra (n>10), the formation becomes unfavourable irrespective of metal.     

The partition-frequency enumeration matrix

The Ramanujan Journal - We develop a calculus that gives an elementary approach to enumerate partition-like objects using an infinite number-theoretic matrix. We call this matrix the...     

Summands of finite group algebras

Czechoslovak Mathematical Journal - We study the inverse problem of the determination of a group algebra from the knowledge of its Wedderburn decomposition. We show that a certain class of matrix...     

Determination of Alendronate Sodium by Box-Behnken Statistical Design

Spectrophotometric and LC methods have been developed and validated for the analysis of alendronate sodium in tablet dosage forms. Methods were based on reaction of the primary amino group of alendronate with ninhydrin reagent in methanolic solution of sodium bicarbonate. The condensed product exhibited UV absorption maximum at 569 nm whereas neither the reagents nor the analyte had any UV absorption. A Box-Behnken statistical design was employed to study the effect of independent variables, ninhydrin (X ₁ ), NaHCO₃ (X ₂ ) and drug concentration (X ₃ ) on dependent variable, absorption via spectrophotometer. From the point prediction tool of design software, it was observed that ninhydrin (0.26%) and NaHCO₃ (0.048 mol L^?1) produced maximum absorption. These optimized parameters were then selected for method validation. The methods obeyed Beer’s law over a selected concentration range with good correlation co-efficient (>0.99). The limit of detection and limit of quantification were 4.5 and 13.75 μg mL^?1 by spectroscopy, and 87 and 263 ng mL^?1 by LC, respectively. Accuracy, precision and % recovery were satisfactory for the proposed method. The method was highly feasible and reproducible for determination of alendronate sodium in bulk powder and pharmaceutical dosage form.     

Theoretical estimation of mesogenic characteristics of 4-methyl (2′-hydroxy,4′-n-hexadecyloxy) azobenzene – a nematic liquid crystal

The compound 4-methyl (2′-hydroxy,4′-n-hexadecyloxy) azobenzene was synthesized by Prajapati and co-workers (Mol. Cryst. Liq. Cryst. 369 (2001), pp. 37–46). Subsequent experiments (D. Pal, [PhD thesis], University of Lucknow, Lucknow, India, 2007) confirmed that the compound exists in nematic phase for a small range of temperature (72°C–80°C). In the present work, optimization of molecular geometry has been carried out by employing the Gaussian 03 suit of programs without any constraint using density functional B3LYP along with 6-31G** basis set and checked for imaginary frequencies. A detailed investigation on intermolecular interaction energy at various interacting configurations has been carried out. In order to study the mesogenic characteristics of the molecule, an attempt has been made to estimate the variation of order parameter with respect to the change in temperature as well as degrees of freedom. These studies will be helpful to understanding the mesogenic character of any molecule prior to synthesis and promises future application in molecular engineering.     

Wetting phenomena at the CO2/water/glass interface

A novel high-pressure apparatus and technique were developed to measure CO2/water/solid contact angles (theta) in situ for pressures up to 204 bar. For two glass substrates with different hydrophilicities, theta increased significantly with CO2 pressure. As the pressure was increased, an increase in the cohesive energy density of CO2 caused the substrate/CO2 and water/CO2 interfacial tensions (gamma) to decrease, whereas the water/substrate gamma value increased. theta for the more hydrophobic substrate was predicted accurately from the experimental water/CO2 gamma value and an interfacial model that included only long-range forces. However, for the more hydrophilic substrate, short-range specific interactions due to capping of the silanol groups by physisorbed CO2 resulted in an unusually large increase in the water/substrate gamma value, which led to a much larger increase in theta than predicted by the model. A novel type of theta hysteresis was discovered in which larger theta values were observed during depressurization than during pressurization, even down to ambient pressure. Effective receding angles were observed upon pressurization, and effective advancing angles were observed upon depressurization on the basis of movement of the three-phase contact line. The greater degree of hysteresis for the more hydrophilic silica can be attributed in part to the capping of silanol groups with CO2. The large effects of CO2 on the various interfacial energies play a key role in the enhanced ability of CO2, relative to many organic solvents, to dry silica surfaces as reported previously on the basis of FTIR spectroscopy (Tripp, C. P.; Combes, J. R. Langmuir 1998, 14, 7348-7352).     

Optimization of process for the production of bio-oil from eucalyptus wood

The pyrolysis of eucalyptus wood was carried out in a batch reactor to optimize the yield of bio-oil.Effect of various parameters like feed(particle) size,temperature,presence of catalyst and heating rate on the yield of bio-oil was investigated.The optimum conditions for high yield of bio-oil are for the particle size 2 mm~5 mm(average l/d=12.84/2.03 mm) at 450 ℃ in high heating rate.The reaction kinetics and the quality of bio-oil produced are independent of the presence of different catalysts like mordenite,kaoline clay,fly ash and silica alumina.The physical properties like odour,colour,PH,viscosity,heating value were determined.The FT-IR analysis of bio-oil indicates the presence of different functional groups such as monomeric alcohol,phenol,ketones,aldehydes,carboxylic acid,amines,and nitro compounds.The composition of the bio-oil at different conditions was analyzed using GC-MS and found that the components are temperature dependent but independent of catalysts used.     

Gene Cloning,Expression, and Characterization of Recombinant Aerolysin from <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Aerolysin is a significant virulent toxin protein secreted by Aeromonas hydrophila; it produces deep wound infections and hemorrhagic septicemia. The complete aerolysin gene (1,482 bp) was amplified from A. hydrophila. Furthermore, it was cloned and expressed into Escherichia coli BL21(DE3) codon plus RP cells using 0.5 mM IPTG for induction. The protein size was 54 kDa as estimated by SDS-PAGE, and it was purified by Ni–NTA affinity chromatography. Anti-His antibodies were used to characterize the expressed aerolysin by Western blotting and showed hemolytic activity with fish red blood cells. Aerolysin may be used as immunoassays for earlier control of A. hydrophila and is also compatible for vaccination.